A breathing apparatus for chemical, biological, radiological and nuclear (CBRN) agents is improved with flexibility, adaptability and modularity. This disclosure includes such benefits arising from an improved hose construction, an improved demand valve, and an improved filter cover.
Crushproof Tubing Company in U.S. Pat. No. 7,431,054 discloses a method of manufacturing a wire reinforced flexible rubber hose for use in breathing air applications. The method comprises positioning a section of wire-reinforced tubing on a forming mandrel and then positioning a sleeve of uncured rubber to cover the section of wire-reinforced tubing. Cording is then wrapped around the sleeve of uncured rubber such that each adjacent wrapping of cording is disposed between and separated by the wire helix of the wire-reinforced tubing. The sleeve of uncured rubber is cured while the cording is wrapped thereon to form a cured hose. The cured hose has a relatively smooth bore. All three plies of the cured hose can be formed from relatively thin walled materials.
Usui Kokusai Sangyo Kaisha Ltd. in U.S. Pat. No. 4,982,765 discloses a flexible composite hose with an inner tube formed from a synthetic resin, an outer tube formed from a thermally shrinkable synthetic resin. The hose has a relatively small wall thickness and carries an adhesive on its inner peripheral surface, and a metal wire interposed spirally between the inner and outer tubes. The adhesive and the thermal shrinkage of the thermally shrinkable resin cause the inner peripheral surface of the outer tube to stick closely to the inner tube and the wire. The outer tube has a spirally corrugated outer peripheral surface defined by the wire. The disclosed materials are Nylon and PVC.